Solid-state image sensor, solid-state imaging device, and camera device

ABSTRACT

The present technology relates to a solid-state image sensor, a solid-state imaging device, and a camera device capable of making white flaws unnoticeable even with a reduced cell size. 
     The solid-state image sensor includes: a register unit formed as an n-type impurity region extending in a first direction; a reading unit configured to read charge from the photoelectric conversion unit into the register unit and formed as a p-type impurity region extending in the same direction as the register unit; a horizontal element isolation unit configured to prevent leakage of charge from the photoelectric conversion unit and formed as a p-type impurity region extending in the same direction as the register unit; and multiple transfer electrodes configured to apply voltage for changing potential distribution of the register unit, wherein a total amount of n-type impurity forming the register unit below a low-level electrode having a standby voltage of a predetermined low value among the transfer electrodes is smaller than a total amount of n-type impurity forming the register unit below a middle-level electrode having a standby voltage higher than the predetermined low value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 andclaims the benefit of PCT Application No. PCT/JP2013/067363 having aninternational filing date of Jun. 25, 2013, which designated the UnitedStates, which PCT application claimed the benefit of Japanese PatentApplication No. 2012-149552 filed Jul. 3, 2012, the disclosures of theabove-identified applications are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present technology relates to a solid-state image sensor, asolid-state imaging device, and a camera device, and in particular to asolid-state image sensor, a solid-state imaging device, and a cameradevice capable of making white flaws unnoticeable even with a reducedcell size.

BACKGROUND ART

Solid-state imaging devices using charge-coupled devices (CCDs) areknown as examples of solid-state imaging devices.

A CCD solid-state image sensor includes multiple photosensor units usingphotoelectric transducers, that is, photodiodes (PDs) configured togenerate and store signal charge of an amount corresponding to theamount of received light, which are arranged in a two-dimensionalmatrix. The signal charge is generated and stored on the basis of lightsignals from a subject incident on the photodiodes of the multiplephotosensor units. The stored signal charge is transferred in thevertical direction by a vertical transfer register arranged for eachcolumn of the photosensor units and transferred in the horizontaldirection by a horizontal transfer register having a CCD structure. Thesignal charge transferred in the horizontal direction is output as imageinformation of the subject from an output unit having a charge-voltageconverter.

A solid-state image sensor has multiple pixels composed of multiplephotosensor units that are photodiodes arranged in horizontal andvertical directions, reading units, and vertical transfer channels, forexample.

Each photosensor unit includes a signal charge storage part and a holeaccumulation region formed in a p-type semiconductor well region of asubstrate made of an n-type semiconductor.

The signal charge storage part is formed by an n-type impurity region.The hole accumulation region is formed by a p-type impurity region (p+)and formed on the surface of the signal charge storage part.

Each vertical transfer channel is formed in the n-type impurity regionat a predetermined distance from the photosensor units. In addition, ap-type impurity region (p) is formed between a vertical transfer channeland a photosensor unit to be read on one side thereof and functions as areading unit. Furthermore, a horizontal element isolation unit made of ap-type impurity region (p+) is formed between the vertical transferchannel and a photosensor unit that is not to be read on the other sidethereof. Furthermore, vertical element isolation units made of p-typeimpurity regions (p+) are formed at both ends of a photosensor unit.

The horizontal element isolation units isolate the respectivephotosensor units in the horizontal direction, and the vertical elementisolation units isolate the respective photosensor units in the verticaldirection. The vertical element isolation units, the horizontal elementisolation units, and the reading units are each formed in contact withthe vertical transfer channels.

First transfer electrodes and second transfer electrodes are formedalternately above the reading units and the vertical transfer channelswith an insulating film therebetween. The vertical transfer channels,the first transfer electrodes, and the second transfer electrodesconstitute the vertical transfer registers.

As a method for forming vertical transfer registers in a microcell, atechnology of allowing the line widths of vertical transfer channels tobe reduced and suppressing occurrence of potential barriers in potentialdistribution of the vertical transfer channels to improve the efficiencyof transferring signal charge has been proposed (refer to PatentDocument 1, for example).

CITATION LIST Patent Documents

Patent Document 1: JP 2010-80791 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Note that, in CCD solid-state image sensors, the influence of whitelines (white flaws) caused in vertical transfer registers on the imagequality has been a concern. The white flaws are caused by crystaldefects of n-type impurity doped as the vertical transfer registers.Thus, to reduce the influence of the white flaws, it is desirable toreduce the amount of n-type impurity doped as the vertical transferregisters.

With the decrease in the cell size in recent years, however, the linewidths of vertical transfer registers and element isolation units aredecreased and impurities are doped at high concentrations to formtransfer channels and the element isolation units. White flaws thus tendto be worse as a result of defects formed at the substrate. Furthermoredark current components from the defects tend to be enhanced owing to anintense electric field at p-n junctions with high concentrations. As aresult, white lines occur more significantly in microcells.

With the conventional technologies as in Patent Document 1, it isdifficult to reduce the total amount of impurity doped into the entirevertical transfer registers, and as a result, sufficient effects ofimproving white lines cannot be produced.

The present technology is disclosed in view of these circumstances, andallows white flaws to be unnoticeable even with a reduced cell size.

Solutions to Problems

A first aspect of the present technology is a solid-state image sensorincluding: a register unit configured to transfer charge stored in aphotoelectric conversion unit and formed as an n-type impurity regionextending in a first direction; a reading unit configured to read chargefrom the photoelectric conversion unit into the register unit and formedas a p-type impurity region extending in the same direction as theregister unit; a horizontal element isolation unit configured to preventleakage of charge from the photoelectric conversion unit and formed as ap-type impurity region extending in the same direction as the registerunit; and multiple transfer electrodes configured to apply voltage forchanging potential distribution of the register unit, wherein a totalamount of n-type impurity forming the register unit below a low-levelelectrode having a standby voltage of a predetermined low value amongthe transfer electrodes is smaller than a total amount of n-typeimpurity forming the register unit below a middle-level electrode havinga standby voltage higher than the predetermined low value.

In the second direction perpendicular to the first direction, a width ofn-type impurity forming the register unit below the low-level electrodemay be smaller than a width of n-type impurity forming the register unitbelow the middle-level electrode.

A concentration of n-type impurity forming the register unit below thelow-level electrode may be lower than a concentration of n-type impurityforming the register unit below the middle-level electrode.

In the second direction perpendicular to the first direction, a highestconcentration position below the low-level electrode may be closer tothe photoelectric conversion unit than a highest concentration positionbelow the middle-level electrode, the highest concentration positionsbeing positions where impurity concentration of the p-type impurityregion forming the reading unit or the horizontal element isolation unitis highest.

Only for highest concentration positions in the p-type impurity regionforming the reading unit among the highest concentration positions, thehighest concentration position below the low-level electrode may becloser to the photoelectric conversion unit than the highestconcentration position below the middle-level electrode.

Only for highest concentration positions in the p-type impurity regionforming the horizontal element isolation unit among the highestconcentration positions, the highest concentration position below thelow-level electrode may be closer to the photoelectric conversion unitthan the highest concentration position below the middle-levelelectrode.

N-type impurity concentration of the sensor unit at a positioncorresponding to that of the low-level electrode may be higher thann-type impurity concentration of the sensor unit at a positioncorresponding to that of the middle-level electrode.

P-type impurity concentration of a surface of the sensor unit at aposition corresponding to that of the low-level electrode may be lowerthan p-type impurity concentration of a surface of the sensor unit at aposition corresponding to that of the middle-level electrode.

A second aspect of the present invention is a solid-state imaging deviceincluding: a register unit configured to transfer charge stored in aphotoelectric conversion unit and formed as an n-type impurity regionextending in a first direction; a reading unit configured to read chargefrom the photoelectric conversion unit into the register unit and formedas a p-type impurity region extending in the same direction as theregister unit; a horizontal element isolation unit configured to preventleakage of charge from the photoelectric conversion unit and formed as ap-type impurity region extending in the same direction as the registerunit; multiple transfer electrodes configured to apply voltage to theregister unit; and a timing generation circuit configured to supplyvoltage to the transfer electrodes to change potential distribution ofthe register unit, wherein a total amount of n-type impurity forming theregister unit below a low-level electrode having a standby voltage of apredetermined low value among the transfer electrodes is smaller than atotal amount of n-type impurity forming the register unit below amiddle-level electrode having a standby voltage higher than thepredetermined low value.

A third aspect of the present invention is a camera device including: asolid state image sensor including: a register unit configured totransfer charge stored in a photoelectric conversion unit and formed asan n-type impurity region extending in a first direction; a reading unitconfigured to read charge from the photoelectric conversion unit intothe register unit and formed as a p-type impurity region extending inthe same direction as the register unit; a horizontal element isolationunit configured to prevent leakage of charge from the photoelectricconversion unit and formed as a p-type impurity region extending in thesame direction as the register unit; and multiple transfer electrodesconfigured to apply voltage for changing potential distribution of theregister unit, wherein a total amount of n-type impurity forming theregister unit below a low-level electrode having a standby voltage of apredetermined low value among the transfer electrodes is smaller than atotal amount of n-type impurity forming the register unit below amiddle-level electrode having a standby voltage higher than thepredetermined low value; an optical system configured to guide incidentlight to the solid state image sensor; and a signal processing circuitconfigured to process an image signal output from a solid-state imagesensor.

The first to third aspects of the present technology include a registerunit configured to transfer charge stored in a photoelectric conversionunit and formed as an n-type impurity region extending in a firstdirection; a reading unit configured to read charge from thephotoelectric conversion unit into the register unit and formed as ap-type impurity region extending in the same direction as the registerunit; a horizontal element isolation unit configured to prevent leakageof charge from the photoelectric conversion unit and formed as a p-typeimpurity region extending in the same direction as the register unit;and multiple transfer electrodes configured to apply voltage forchanging potential distribution of the register unit, wherein a totalamount of n-type impurity forming the register unit below a low-levelelectrode having a standby voltage of a predetermined low value amongthe transfer electrodes is smaller than a total amount of n-typeimpurity forming the register unit below a middle-level electrode havinga standby voltage higher than the predetermined low value.

Effects of the Invention

According to the present technology, white flaws can be made to beunnoticeable even with a reduced cell size.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration according toan embodiment of a solid-state imaging device to which the presenttechnology is applied.

FIG. 2 is a plan view showing an example configuration of a conventionalimaging unit.

FIGS. 3A and 3B show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 2.

FIG. 4 is a timing chart of charge transfer when a moving image iscaptured by the solid-state imaging device.

FIG. 5 is an enlarged chart of waveforms of transfer clock signals inFIG. 4.

FIG. 6 is a chart showing potentials of transfer electrodes atrespective times in FIG. 5.

FIG. 7 is a graph showing the relation between a white line and alow-level voltage.

FIG. 8 is a graph showing the relation between a white line and amiddle-level voltage.

FIG. 9 is a plan view showing an example configuration of an imagingunit according to an embodiment of the present technology.

FIGS. 10A to 10D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 9.

FIGS. 11A and 11B show cross-sectional views for explaining theconfiguration of an imaging unit on a completed substrate.

FIG. 12 is a graph for explaining variation in impurity concentration.

FIG. 13 is a plan view showing an example configuration of an imagingunit according to another embodiment of the present technology.

FIGS. 14A to 14D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 13.

FIG. 15 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIGS. 16A to 16D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 15.

FIG. 17 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIGS. 18A to 18D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 17.

FIG. 19 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIGS. 20A to 20D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 19.

FIG. 21 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIGS. 22A to 22D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 21.

FIG. 23 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIGS. 24A to 24D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 23.

FIG. 25 is a cross-sectional view along a dashed-dotted line E-E′ inFIG. 23.

FIGS. 26A and 26B show cross-sectional views for explaining theconfiguration of an imaging unit on a completed substrate.

FIG. 27 is a graph for explaining variation in impurity concentration.

FIG. 28 is a cross-sectional view for explaining another configurationof an imaging unit on a completed substrate.

FIG. 29 is a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.

FIG. 30 is a timing chart of charge transfer when a static image iscaptured by the solid-state imaging device.

FIG. 31 is an enlarged chart of waveforms of transfer clock signals inFIG. 30.

FIG. 32 is a chart showing potentials of transfer electrodes atrespective times in FIG. 31.

FIG. 33 is a block diagram showing an example configuration of a cameradevice that is an electronic device to which the present technology isapplied.

MODES FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing a schematic configuration according toan embodiment of a solid-state imaging device to which the presenttechnology is applied. The solid-state imaging device 10 shown in FIG. 1includes a CCD image sensor 11 and a timing generation circuit 12.

The CCD image sensor 11 includes an imaging unit 22, a horizontaltransfer register 23, and an output unit 24. The output unit 24 has acharge-voltage converter formed by a floating gate, for example.

The imaging unit 22 includes a large number of pixels composed of sensorunits configured to perform photoelectric conversion, vertical transferregisters shown on the left side of the sensor units, and reading unitsconfigured to read signal charge stored in the sensor units (lightreceiving units) into the vertical transfer registers, which arearranged in a two-dimensional matrix.

The respective pixels are isolated by horizontal element isolation units(channel stoppers), which are not shown, so as not to electricallyinterfere with one another. Each vertical transfer register is shared bysensor units of each column, and a predetermined number of verticaltransfer registers are arranged in the row direction. Vertical elementisolation units, which are not shown, are also provided between therespective sensor units arranged in the vertical direction in FIG. 1, sothat the sensor units do not electrically interfere with one another.

The imaging unit 22 receives as input vertical transfer clock signalsφV1 to φV8 to drive the vertical transfer registers. The horizontaltransfer register receives as input horizontal transfer clock signalsφH1 and φH2 to drive the horizontal transfer register. The verticaltransfer clock signals φV1 to φV8 and the horizontal transfer clocksignals φH1 and φH2 are generated by the timing generation circuit 12.

The vertical transfer registers and the horizontal transfer register areeach formed by a potential well for minority carriers formed as a resultof introduction of impurity into a semiconductor substrate on the sideof the surface and multiple electrodes (transfer electrodes) formed in arepeated manner and isolated on the substrate with an insulating filmtherebetween. The potential well for minority carriers mentioned aboveis also referred to as a “transfer channel.”

The transfer clock signals (φV1 to φV8 or φH1 and φH2) described aboveare applied to the transfer electrodes of the vertical transferregisters and the horizontal transfer register with phases shiftedperiodically. The vertical transfer registers and the horizontaltransfer register are controlled by the transfer clock signals appliedto the transfer electrodes so that the potential distribution of thepotential well changes sequentially, and function as what are calledshift registers configured to transfer the charges in the potential wellin the phase shift direction of the transfer clock signals.

The transfer electrodes are provided correspondingly to the respectivesensor units and vertical element isolation units.

Next, a detailed configuration of the imaging unit 22 will be described.

FIG. 2 is an enlarged view of part of the imaging unit 22 in FIG. 1 in aform of a plan view showing an example configuration of a conventionalimaging unit. In fact, FIG. 2 shows a shape of a mask used in amanufacturing process for attaching impurity to the substrate, and theconfiguration of the imaging unit on a completed substrate variesslightly according to the manufacturing process of the substrate.

In the example of FIG. 2, sensor units 108 formed as n-type impurityregions are arranged in the vertical direction in FIG. 2. In thisexample, two columns, which are a left column and a right column, ofsensor units 108 are arranged. Note that a p-type impurity region isformed on the front surface (light receiving side) of each sensor unit108 and a p-type impurity region (p-type well) is also formed on thebottom surface (substrate side) of the sensor unit 108.

A vertical element isolation unit 102 formed as a p-type impurity regionis formed between sensor units adjacent to each other in the verticaldirection in FIG. 2.

In addition, a reading unit 103 formed as a p-type impurity region isformed on the left side in FIG. 2 of each sensor unit 108.

Furthermore, a vertical transfer register 101 formed as an n-typeimpurity region is formed on the left side in FIG. 2 of each readingunit 103.

A horizontal element isolation unit 104 formed as a p-type impurityregion is formed on the left side in FIG. 2 of each vertical transferregister 101.

Thus, each sensor 108 that is an n-type impurity region is surrounded bya reading unit 103 on the left side and a horizontal element isolationunit 104 on the right side, which are p-type impurity regions, andvertical element isolation units 102 on the upper and lower sides, whichare p-type impurity regions. In this manner, each of the sensors 108that are n-type impurity regions surrounded by p-type impurity regionsconstitutes a pixel arranged in the imaging unit 22.

Furthermore, the transfer electrodes described above are provided on theleftmost side in FIG. 2. As described above, transfer electrodes 105-1to 105-8 are provided correspondingly to the respective sensor units andvertical element isolation units. In other words, the transferelectrodes 105-1 to 105-8 are provided at the same positions in thevertical direction as those of the respective sensor units 108 and therespective vertical element isolation units 102.

When the transfer electrodes 105-1 to 105-8 need not be individuallydistinguished, the transfer electrodes will be simply referred to astransfer electrodes 105.

Although the transfer electrodes 105 are shown only on the leftmost sidein FIG. 2, the transfer electrodes 105 extend in the horizontaldirection in FIG. 2.

FIGS. 3A and 3B show cross-sectional views along dashed-dotted linesA-A′ and B-B′ in FIG. 2. FIG. 3A is a cross-sectional view along thedashed-dotted line A-A′ in FIG. 2 and FIG. 3B is a cross-sectional viewalong the dashed-dotted line B-B′ in FIG. 2.

As shown in FIG. 3A, the transfer electrode 105-2 extends over thevertical element isolation units 102. In contrast, as shown in FIG. 3B,the transfer electrode 105-3 is not arranged over the sensor units 108.

Furthermore, as shown in FIG. 3B, a p-type impurity region 107 is formedon the front surface (light receiving side) of each sensor unit 108 anda p-type well 109 is formed on the bottom surface (substrate side) ofthe sensor unit 108.

As shown in FIGS. 3A and 3B, the transfer electrodes 105, the verticaltransfer registers 101, the reading units 103, the horizontal elementisolation units 104, and the like are formed on the substrate 110, andan insulating film 106 is arranged immediately under the transferelectrodes 105.

FIG. 4 is a timing chart of charge transfer when a moving image iscaptured by the solid-state imaging device 10. In the example of FIG. 4,waveforms of the transfer clock signals φV1 to φV8 are shown. In FIG. 4,vertical lines actually represent pulses of the signals.

The waveforms of the transfer clock signals φV1 to φV8 change to voltagevalues of H (high-level voltage), M (middle-level voltage), and L(low-level voltage). For each of the signals, a part represented by ahorizontal line corresponds to a standby voltage.

The middle-level voltage is a voltage of approximately 0 V, thehigh-level voltage is a positive voltage, and the low-level voltage is anegative voltage. Thus, when absolute values of voltages are referredto, the middle-level voltage has a small value and the high-levelvoltage and the low-level voltage have large values.

As shown in FIG. 4, the transfer clock signals φV1 to φV8 are applied tothe transfer electrodes with phases shifted periodically. The verticaltransfer registers are controlled by the transfer clock signals appliedto the transfer electrodes so that the potential distribution of thepotential well changes sequentially, and function as what are calledshift registers configured to transfer the charges in the potential wellin the phase shift direction of the transfer clock signals.

FIG. 5 is an enlarged chart of the waveforms of the transfer clocksignals φV1 to φV8 in FIG. 4 immediately after the transfer clock signalφV1 has become H and charges are read from the sensor units 108 into thevertical transfer registers 101, for example. In this example, thewaveforms of the transfer clock signals φV1 to φV8 at time t0 to time t8are shown. As shown in FIG. 5, the transfer clock signals φV1 to φV8 arepulsed with shifted phases.

FIG. 6 is a chart showing potentials of the transfer electrodes at timet0 to time t8 in FIG. 5. Note that the transfer electrodes to which thetransfer clock signals φV1 to φV8 are applied are referred to astransfer electrodes V1 to V8, respectively. In FIG. 6, parts shown bythick black horizontal lines represent the potential well, and partsshown as white projections represent potential barriers.

In this manner, the potential distribution of the potential wellsequentially changes under the control of the transfer clock signals φV1to φV8 applied to the transfer electrodes V1 to V8, respectively. Thecharge in the potential well is thus transferred in the phase shiftdirection of the transfer clock signals.

Among the transfer electrodes V1 to V8, a transfer electrode to which atransfer clock signal having a standby voltage L is applied will bereferred to as a VL electrode and a transfer electrode to which atransfer clock signal having a standby voltage M is applied will bereferred to as a VM electrode. In the example shown in FIG. 4, thestandby voltages of the transfer clock signals φV1 and φV8 are L. Thetransfer electrodes V1 and V8 are thus referred to VL electrodes, andthe transfer electrodes V2 to V7 are referred to as VM electrodes.

In the example of FIG. 2, the second transfer electrode 105-2 from thetop and the third transfer electrode 105-3 from the top in FIG. 2 are VLelectrodes and the other transfer electrodes are VM electrodes.

Note that, in solid-state image sensors such as CCD image sensors, theinfluence of white lines (white flaws) caused in vertical transferregisters on the image quality is a concern. The white flaws are causedby crystal defects of n-type impurity doped as the vertical transferregisters. Thus, to reduce the influence of the white flaws, it isdesirable to reduce the amount of n-type impurity doped as the verticaltransfer registers.

The potential of the n-type regions (vertical transfer registers),however, needs to be sufficiently deep correspondingly to the chargeamount that can be handled by the vertical transfer registers. Thus, thelevel of potential corresponding to the charge amount handled by thevertical transfer registers cannot be obtained only by simply reducingthe amount of doped n-type impurity.

A method of increasing the widths of the n-type regions (that is, theline widths of the vertical transfer registers) to obtain the potentiallevel corresponding to the handled charge amount, for example, is thusconceivable. The increase in the line widths of the vertical transferregisters allow a sufficient handled charge amount to be ensured evenwith a shallow potential and the amount of impurity in the verticaltransfer registers to be reduced. Furthermore, the increase in the linewidths of the vertical transfer registers makes the vertical transferregisters be less likely to be affected by dispersion of impurity fromthe p-type impurity regions of the adjacent reading units and verticalelement isolation units and can reduce the amount of doped n-typeimpurity required for obtaining a desired potential.

In recent years, however, the pixel size of solid-state image sensorsuch as CCD image sensors has been becoming smaller and smaller, and itis difficult to change design to further increase the widths of verticaltransfer registers in such circumstances. Furthermore, the areas of thelight receiving surfaces of sensor units may become smallercorrespondingly to the increase in the line widths of vertical transferregisters, and there is a concern about influence of reduction insensitivity, reduction in saturated signal amount, or the like on theimage quality.

Furthermore, it was shown by experiments that a white line (white flaw)correlates highly with a low-level voltage. FIG. 7 is a graph showingthe relation between a white line and a low-level voltage. In FIG. 7,the horizontal axis represents a low-level voltage value, the verticalaxis represents a white line output level, and variations in the whiteline output level with a variation in the low-level voltage are shown bya line 201 and a line 202.

The line 201 shows the variation in the white line output level with thevariation in the low-level voltage in the case of a good white line(non-defective white line) that has little influence on the imagequality. The line 202 shows the variation in the white line output levelwith the variation in the low-level voltage in the case of a white line(defective white line) that has influence on the image quality.

As shown by the line 202 in FIG. 7, the white line output level ishigher as the low-level voltage value is lower. Thus, the image qualityis more degraded by a white flaw as the low-level voltage value islower. In the case of the line 201, the white line output level isapproximately constant independently of the variation in the low-levelvoltage.

FIG. 8 is a graph showing the relation between a white line and amiddle-level voltage. In FIG. 8, the horizontal axis represents a middlelevel voltage value, the vertical axis represents a white line outputlevel, and variations in the white line output level with a variation inthe middle-level voltage are shown by a line 203 and a line 204.

The line 203 shows the variation in the white line output level with thevariation in the middle-level voltage in the case of a good white line(non-defective white line) that has little influence on the imagequality. The line 204 shows the variation in the white line output levelwith the variation in the middle-level voltage in the case of a whiteline (defective white line) that has influence on the image quality.

Unlike FIG. 7, the white line output level is approximately constantindependently of the variation in the middle-level voltage in the casesof the lines 203 and 204.

As can be seen in FIGS. 7 and 8, occurrence of white flaws havinginfluence on the image quality correlates highly with the variation inthe low-level voltage. This is considered to be because the filedintensity becomes high when a low-level voltage is applied, whichfacilitates generation of dark current.

The present technology can reduce the influence of white flaws withoutpreventing the decrease in the pixel size of solid-state image sensors.

FIG. 9 is an enlarged view of part of the imaging unit 22 in FIG. 1 in aform of a plan view showing an example configuration of an imaging unitaccording to an embodiment of the present technology. FIGS. 10A to 10Dshow cross-sectional views along dashed-dotted lines A-A′, B-B′, C-C′and D-D′ in FIG. 9. FIG. 10A is a cross-sectional view along thedashed-dotted line A-A′ in FIG. 2 and FIG. 10B is a cross-sectional viewalong the dashed-dotted line B-B′ in FIG. 9. Furthermore, FIG. 10C is across-sectional view along the dashed-dotted line C-C′ in FIG. 9 andFIG. 10D is a cross-sectional view along the dashed-dotted line D-D′ inFIG. 9.

In fact, FIG. 9 shows a shape of a mask used in a manufacturing processfor attaching impurity to the substrate, and the completed configurationof the imaging unit on the substrate varies slightly according to themanufacturing process of the substrate.

In FIG. 9, parts corresponding to those in FIG. 2 are designated by thesame reference numerals. Similarly, in FIG. 10, parts corresponding tothose in FIGS. 3A and 3B are designated by the same reference numerals.

In the example of FIGS. 9 and 10, unlike FIGS. 2 and 3, each verticaltransfer register 101 has a smaller width below the transfer electrodes105-2 and 105-3 that are VL electrodes.

For example, in FIG. 9, the width in the horizontal direction of eachvertical transfer register 101 has a width W11 at the uppermost portionand the lowermost portion in FIG. 9 but becomes thinner to have a widthW12 at a portion at substantially the same position in the verticaldirection as the upper end of the transfer electrode 105-2 in FIG. 9.The vertical transfer register 101 extends while maintaining the widthW12 and becomes thicker to have the original width W11 at a portion atsubstantially the same position in the vertical direction as the lowerend of the transfer electrode 105-3 in FIG. 9.

In addition, for example, the width W12 in the horizontal direction ofthe vertical transfer register 101 in FIG. 10A is smaller than the widthW11 in the horizontal direction of the vertical transfer register 101 inFIG. 10C. Furthermore, the width W12 in the horizontal direction of thevertical transfer register 101 in FIG. 10B is smaller than the width W11in the horizontal direction of the vertical transfer register 101 inFIG. 10D. In contrast, the widths (thicknesses) in the verticaldirection of the vertical transfer register 101 are all the same inFIGS. 10A to 10D.

Furthermore, in the example of FIGS. 9 and 10, unlike FIGS. 2 and 3,each reading unit 103 and each horizontal element isolation unit 104 arecurved toward the center of the sensor unit 108 below the transferelectrodes 105-2 and 105-3 that are VL electrodes.

For example, in FIG. 9, the position in the horizontal direction of thecenter of the reading unit 103 is the position shown by a dashed-dottedline 151 at the upper end and the lower end thereof in FIG. 9. Thecenter of the reading unit 103, however, curves rightward in FIG. 9 at aportion at substantially the same position in the vertical direction asthe upper end of the transfer electrode 105-2 in FIG. 9 and comes to theposition shown by a dashed-dotted line 152. The center of the readingunit 103 then extends along the position shown by the dashed-dotted line152 and curves leftward in FIG. 9 at the portion at substantially thesame position in the vertical direction as the lower end of the transferelectrode 105-3 in FIG. 9 back to the original position (the positionshown by the dashed-dotted line 151).

In addition, in FIG. 9, the position in the horizontal direction of thecenter of the horizontal element isolation unit 104 is the positionshown by a dashed-dotted line 153 at the upper end and the lower endthereof in FIG. 9, for example. The center of the horizontal elementisolation unit 104, however, curves leftward in FIG. 9 at a portion atsubstantially the same position in the vertical direction as the upperend of the transfer electrode 105-2 in FIG. 9 and comes to the positionshown by a dashed-dotted line 154. The center of the horizontal elementisolation unit 104 then extends along the position shown by thedashed-dotted line 154 and curves rightward in FIG. 9 at the portion atsubstantially the same position in the vertical direction as the lowerend of the transfer electrode 105-3 in FIG. 9 back to the originalposition (the position shown by the dashed-dotted line 153).

In addition, for example, the width W21 in the horizontal direction ofthe vertical element isolation unit 102 in FIG. 10A is smaller than thewidth W22 in the horizontal direction of the vertical element isolationunit 102 in FIG. 10C. Thus, as described above with reference to FIG. 9,since the reading unit 103 and the horizontal element isolation unit 104curve toward the center of the sensor unit 108, the width in thehorizontal direction in FIG. 9 of the vertical element isolation unit102 becomes smaller at the position of the dashed-dotted line A-A′.

Furthermore, the position in the horizontal direction of the center ofthe reading unit 103 in FIG. 10B is shifted rightward from the positionin the horizontal direction of the center of the reading unit 103 inFIG. 10D. The position in the horizontal direction of the center of thehorizontal element isolation unit 104 in FIG. 10B is shifted leftwardfrom the position in the horizontal direction of the center of thehorizontal element isolation unit 104 in FIG. 10D. In contrast, thewidths in the horizontal direction of the reading unit 103 and thehorizontal element isolation unit 104 are the same in FIGS. 10B and 10D.

Furthermore, as described above, FIG. 9 in fact shows a shape of a maskused in a manufacturing process for attaching impurity to the substrate,and the configuration of the imaging unit on the completed substratevaries slightly according to the manufacturing process of the substrate.Thus, in the process of manufacturing the substrate, the n-type impurityforming the vertical transfer registers 101 and the p-type impurityforming the reading units 103, the vertical element isolation units 102,and the horizontal element isolation units 104 disperse. Thecross-sectional views shown in FIGS. 10A to 10D are drawn regardless ofthe impurity dispersion in the manufacturing process for simplicity, andthe cross-sectional views of the completed imaging unit on the substratetaking the impurity dispersion into consideration are slightly differentfrom those shown in FIG. 10.

FIGS. 11A and 11B show cross-sectional views for explaining theconfiguration of an imaging unit on a completed substrate takingimpurity dispersion in the manufacturing process into consideration.FIG. 11A is a cross-sectional view along the dashed-dotted line B-B′ inFIG. 9 and corresponds to FIG. 10B. FIG. 11B is a cross-sectional viewalong the dashed-dotted line D-D′ in FIG. 9 and corresponds to FIG. 10D.

While each vertical transfer register 101 and each reading unit 103 aredrawn as being arranged separately from each other in FIGS. 10B and 10D,each vertical transfer register 101 and each reading unit 103 are drawnas being in contact with each other in FIGS. 11A and 11B. Furthermore,while each vertical transfer register 101 and each horizontal elementisolation unit 104 are drawn as being arranged separately from eachother in FIGS. 10B and 10D, each vertical transfer register 101 and eachhorizontal element isolation unit 104 are drawn as being in contact witheach other in FIGS. 11A and 11B.

Thus, as a result of impurity dispersion in the manufacturing process,the n-type impurity regions (vertical transfer registers 101) and thep-type impurity regions (reading units 103 and horizontal elementisolation units 104) have dispersed. When impurity is attached by usingthe mask as shown in FIG. 9, however, the concentration of n-typeimpurity is high at the center of the line of each vertical transferregister 101 and becomes lower toward both ends thereof, for example.Furthermore, the concentration of p-type impurity is high at the centerof the line of each reading unit 103 or each horizontal elementisolation unit 104 and becomes lower toward both ends thereof.

In FIG. 11, the state in which the concentration of n-type impurity ishigh at the center of the line of the vertical transfer register 101 andbecomes lower toward both ends thereof is expressed by a gradation.Similarly, the state in which the concentration of p-type impurity ishigh at the center of the line of the reading unit 103 or the horizontalelement isolation unit 104 and becomes lower toward both ends thereof isexpressed by a gradation.

FIG. 12 is a graph explaining variation in the impurity concentrationdescribed above. In FIG. 12, the horizontal axis represents the positionin the horizontal direction in FIGS. 11A and 11B and the vertical axisrepresents the impurity concentration.

In FIG. 12, a solid line 211 represents variation in the concentrationof n-type impurity at a dashed-dotted line F-F′ in FIG. 11A, and adotted line 212 represents variation in the concentration of n-typeimpurity at a dashed-dotted line G-G′ in FIG. 11B.

The solid line 211 changes more sharply than the dotted line 212.Specifically, the solid line 211 and the dotted line 212 both form peaksat the center in FIG. 12 and incline leftward and rightward therefrom,and the inclination of the solid line 211 is sharper.

Note that the concentration of n-type impurity around the center in FIG.12 represents the concentration of n-type impurity of the verticaltransfer register 101, and the concentrations of n-type impurity aroundthe left and right ends in FIG. 12 represent the concentrations ofn-type impurity of the sensor units 108.

Furthermore, in FIG. 12, a solid line 213 represents variation in theconcentration of p-type impurity at the dashed-dotted line F-F′ in FIG.11A, and a dotted line 214 represents variation in the concentration ofp-type impurity at the dashed-dotted line G-G′ in FIG. 11B. Note thatthe solid line 213 and the dotted line 214 represent the concentrationsof p-type impurity of the horizontal element isolation unit 104.

The solid line 213 changes more sharply than the dotted line 214.Specifically, the solid line 213 and the dotted line 214 both form peaksat a point on the left side in FIG. 12 and incline gently leftward andrightward therefrom, and the inclination of the solid line 213 issharper.

Furthermore, in FIG. 12, a solid line 215 represents variation in theconcentration of p-type impurity at the dashed-dotted line F-F′ in FIG.11A, and a dotted line 216 represents variation in the concentration ofp-type impurity at the dashed-dotted line G-G′ in FIG. 11B. Note thatthe solid line 215 and the dotted line 216 represent the concentrationsof p-type impurity of the reading unit 103.

The solid line 215 changes more sharply than the dotted line 216.Specifically, the solid line 215 and the dotted line 216 both form peaksat a point on the right side in FIG. 12 and incline gently leftward andrightward therefrom, and the inclination of the solid line 215 issharper.

With the configuration of the imaging unit 22 as described above withreference to FIGS. 9 to 11, the influence of white flaws can be reducedwithout preventing the decrease in the pixel size of solid-state imagesensors.

Specifically, according to the present technology, the line widths ofthe vertical transfer registers are made smaller below the VL electrodeswhere occurrence of white flaws having influence on the image quality issignificant. As a result, the amount of doped n-type impurity below VLelectrodes is reduced and the amount of n-type impurity per unit areabecomes smaller below the VL electrodes on the completed substrate,which can suppress occurrence of white flaws having influence on theimage quality. Thus, the total amount of n-type impurity below the VLelectrodes is reduced.

At the same time, with the present technology, the centers of the linesof the reading units 103 and the horizontal element isolation units 104are farther from the vertical transfer registers below the VLelectrodes. As a result, the vertical transfer registers 101 become lesslikely to be influenced by dispersion of p-type impurity of the adjacentreading units 103 and horizontal element isolation units 104, and thepotential can be made sufficiently deep even with the reduced amount ofdoped n-type impurity. Thus, a desired potential can be obtained evenwhen the line widths of the vertical transfer registers 101 are reduced.

Furthermore, according to the present technology, some of the areas ofthe light receiving surfaces of the sensor units 108 are reduced as aresult of arranging the centers of the lines of the reading units 103and the horizontal element isolation units 104 farther from the verticaltransfer registers. The areas of the light receiving surfaces, however,are only reduced at the sensor units 108 arranged below the VLelectrodes, and the areas of the light receiving surfaces of the othersensor units are not changed. Thus, the influence of reduction insensitivity, reduction in saturated signal amount, or the like on theimage quality is very limited.

FIG. 13 is an enlarged view of part of the imaging unit 22 in FIG. 1 ina form of a plan view showing an example configuration of an imagingunit according to another embodiment of the present technology. FIGS.14A to 14D show cross-sectional views along dashed-dotted lines A-A′,B-B′, C-C′ and D-D′ in FIG. 13. FIG. 14A is a cross-sectional view alongthe dashed-dotted line A-A′ in FIG. 13 and FIG. 14B is a cross-sectionalview along the dashed-dotted line B-B′ in FIG. 13. Furthermore, FIG. 14Cis a cross-sectional view along the dashed-dotted line C-C′ in FIG. 13and FIG. 14D is a cross-sectional view along the dashed-dotted line D-D′in FIG. 13.

In fact, FIGS. 14A to 14D show a shape of a mask used in a manufacturingprocess for attaching impurity to the substrate, and the configurationof the imaging unit on a completed substrate varies slightly accordingto the manufacturing process of the substrate.

In FIG. 13, parts corresponding to those in FIG. 9 are designated by thesame reference numerals. Similarly, in FIG. 14, parts corresponding tothose in FIGS. 10A to 10D are designated by the same reference numerals.

In the configuration shown in FIGS. 13 and 14, unlike the configurationdescribed above with reference to FIGS. 9 and 10, the vertical transferregister 101 has a smaller line width in such a shape that only the leftside thereof is cut off below the transfer electrodes 105-2 and 105-3that are VL electrodes.

For example, in FIG. 13, the width in the horizontal direction of thevertical transfer register 101 has a width W11 at the uppermost portionand the lowermost portion in FIG. 13 but becomes thinner only at theleft side thereof to have a width W13 at a portion at substantially thesame position in the vertical direction as the upper end of the transferelectrode 105-2 in FIG. 13. The vertical transfer register 101 thenextends while maintaining the width W13 and becomes thicker to have theoriginal width W11 at a portion at substantially the same position inthe vertical direction as the lower end of the transfer electrode 105-3in FIG. 13.

In addition, for example, the width W13 in the horizontal direction ofthe vertical transfer register 101 in FIG. 14A is smaller than the widthW11 in the horizontal direction of the vertical transfer register 101 inFIG. 14C. Furthermore, the width W13 in the horizontal direction of thevertical transfer register 101 in FIG. 14B is smaller than the width W11in the horizontal direction of the vertical transfer register 101 inFIG. 14D. In contrast, the widths (thicknesses) in the verticaldirection of the vertical transfer register 101 are all the same inFIGS. 14A to 14D.

Furthermore, in the example of FIGS. 13 and 14, unlike the example ofFIGS. 9 and 10, only the horizontal element isolation unit 104 is curvedtoward the center of the sensor unit 108 below the transfer electrodes105-2 and 105-3 that are VL electrodes.

For example, in FIG. 13, the position in the horizontal direction of thecenter of the horizontal element isolation unit 104 is the positionshown by a dashed-dotted line 153 at the upper end and the lower endthereof in FIG. 13. The center of the horizontal element isolation unit104, however, curves leftward in FIG. 13 at a portion at substantiallythe same position in the vertical direction as the upper end of thetransfer electrode 105-2 in FIG. 13 and comes to the position shown by adashed-dotted line 154. The center of the horizontal element isolationunit 104 then extends along the position shown by the dashed-dotted line154 and curves rightward in FIG. 13 at the portion at substantially thesame position in the vertical direction as the lower end of the transferelectrode 105-3 in FIG. 13 back to the original position (the positionshown by the dashed-dotted line 153).

In addition, for example, the width W23 in the horizontal direction ofthe vertical element isolation unit 102 in FIG. 14A is smaller than thewidth W22 in the horizontal direction of the vertical element isolationunit 102 in FIG. 14C. Thus, as described above with reference to FIG.13, since the horizontal element isolation unit 104 curves toward thecenter of the sensor unit 108, the width in the horizontal direction inFIG. 13 of the vertical element isolation unit 102 becomes smaller atthe position of the dashed-dotted line A-A′.

Furthermore, the position in the horizontal direction of the center ofthe horizontal element isolation unit 104 in FIG. 14B is shiftedleftward from the position in the horizontal direction of the center ofthe horizontal element isolation unit 104 in FIG. 14D. In contrast, thewidths in the horizontal direction of the reading unit 103 and thehorizontal element isolation unit 104 are the same in FIGS. 14B and 14D.

Furthermore, as described above, FIG. 13 in fact shows a shape of a maskused in a manufacturing process for attaching impurity to the substrate,and the configuration of the imaging unit on the completed substratevaries slightly according to the manufacturing process of the substrate.Thus, in the process of manufacturing the substrate, the n-type impurityforming the vertical transfer registers 101 and the p-type impurityforming the reading units 103, the vertical element isolation units 102,and the horizontal element isolation units 104 disperse. Thecross-sectional views shown in FIGS. 14A to 14D are drawn regardless ofthe impurity dispersion in the manufacturing process for simplicity, andthe cross-sectional views of the completed imaging unit on the substratetaking the impurity dispersion into consideration are slightly differentfrom those shown in FIG. 14.

Specifically, similarly to the case described above with reference toFIGS. 11, 12, etc., the vertical transfer registers 101 and thehorizontal element isolation units 104 are arranged in contact with oneanother while the concentration of n-type impurity and the concentrationof p-type impurity are varied on the completed substrate.

With the configuration of the imaging unit 22 as described above withreference to FIGS. 13 to 14, the influence of white flaws can still bereduced without preventing the decrease in the pixel size of solid-stateimage sensors.

Specifically, with the configuration of FIGS. 13 and 14, the line widthsof the vertical transfer registers are made smaller below the VLelectrodes where occurrence of white flaws having influence on the imagequality is significant. As a result, the amount of doped n-type impuritybelow the VL electrodes is reduced and the amount of n-type impurity perunit area becomes smaller below the VL electrodes on the completedsubstrate, which can suppress occurrence of white flaws having influenceon the image quality. Thus, the total amount of n-type impurity belowthe VL electrodes is reduced.

At the same time, the centers of the lines of the horizontal elementisolation units 104 are farther from the vertical transfer registersbelow the VL electrodes. As a result, the vertical transfer registers101 become less likely to be influenced by dispersion of p-type impurityof the adjacent horizontal element isolation units 104, and thepotential can be made sufficiently deep even with the reduced amount ofdoped n-type impurity. Thus, a desired potential can be obtained evenwhen the line widths of the vertical transfer registers 101 are reduced.

The line widths W13 of the vertical transfer registers 101 under the VLelectrodes in the configuration of FIGS. 13 and 14, however, are largerthan the line widths W12 of the vertical transfer registers 101 underthe VL electrodes in the configuration of FIGS. 9 and 10. Thus, ascompared to the configuration of FIGS. 9 and 10, the amount of dopedn-type impurity is slightly increased and the effect of suppressingoccurrence of white flaws having influence on the image quality isslightly reduced in the configuration of FIGS. 13 and 14.

In contrast, as compared to the configuration of FIGS. 9 and 10, theamount by which the areas of the light receiving surfaces of the sensorunits 108 below the VL electrodes are reduced is smaller in theconfiguration of FIGS. 13 and 14. Thus, the influence of reduction insensitivity, reduction in saturated signal amount, or the like on theimage quality is further limited.

In FIGS. 13 and 14, an example in which each vertical transfer register101 has a smaller line width in such a shape that only the left sidethereof is cut off and only each horizontal element isolation unit 104curves toward the center of the sensor unit 108 has been explained.

However, each vertical transfer register 101 may have a smaller linewidth in such a shape that only the right side thereof in FIGS. 13 and14 is cut off and only each reading unit 103 may curve toward the centerof the sensor unit 108. A configuration in this case is shown in FIGS.15 and 16.

FIG. 15 is an enlarged view of part of the imaging unit 22 in FIG. 1 ina form of a plan view showing an example configuration of an imagingunit according to another embodiment of the present technology. FIGS.16A to 16D show cross-sectional views along dashed-dotted lines A-A′,B-B′, C-C′ and D-D′ in FIG. 15. FIG. 16A is a cross-sectional view alongthe dashed-dotted line A-A′ in FIG. 15 and FIG. 16B is a cross-sectionalview along the dashed-dotted line B-B′ in FIG. 15. Furthermore, FIG. 16Cis a cross-sectional view along the dashed-dotted line C-C′ in FIG. 15and FIG. 16D is a cross-sectional view along the dashed-dotted line D-D′in FIG. 15.

In fact, FIG. 15 shows a shape of a mask used in a manufacturing processfor attaching impurity to the substrate, and the configuration of theimaging unit on a completed substrate varies slightly according to themanufacturing process of the substrate. Specifically, similarly to thecase described above with reference to FIGS. 11, 12, etc., the verticaltransfer registers 101 and the reading units 103 are arranged in contactwith one another while the concentration of n-type impurity and theconcentration of p-type impurity are varied on the completed substrate.

As described above, in the configuration shown in FIGS. 15 and 16, eachvertical transfer register 101 has a smaller line width in such a shapethat only the right side thereof in FIGS. 15 and 16 is cut off and onlyeach reading unit 103 curves toward the center of the sensor unit 108.As a result, the same effects as those of the configuration of FIGS. 13and 14 can still be produced.

In the example described above with reference to FIGS. 9 and 10, anexample in which each vertical transfer register has a smaller linewidth and the centers of the lines of each reading unit 103 and eachhorizontal element isolation unit 104 are arranged farther from thevertical transfer register below VL electrodes has been described. Inthis case, however, the areas of the light receiving surfaces of thesensor unit 108 below the VL electrodes are reduced as described above.

For example, if each vertical transfer register has a smaller line widthand each reading unit 103 and each horizontal element isolation unit 104also have smaller line widths below the VL electrodes, the areas of thelight receiving surfaces of the sensor units 108 can be maintained. Aconfiguration in this case is shown in FIGS. 17 and 18.

FIG. 17 is an enlarged view of part of the imaging unit 22 in FIG. 1 ina form of a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.FIGS. 18A to 18D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 17. FIG. 18A is a cross-sectional viewalong the dashed-dotted line A-A′ in FIG. 17 and FIG. 18B is across-sectional view along the dashed-dotted line B-B′ in

FIG. 17. Furthermore, FIG. 18C is a cross-sectional view along thedashed-dotted line C-C′ in FIG. 17 and FIG. 18D is a cross-sectionalview along the dashed-dotted line D-D′ in FIG. 17.

In fact, FIG. 17 shows a shape of a mask used in a manufacturing processfor attaching impurity to the substrate, and the configuration of theimaging unit on a completed substrate varies slightly according to themanufacturing process of the substrate. Specifically, similarly to thecase described above with reference to FIGS. 11, 12, etc., each verticaltransfer register 101 is arranged in contact with both of a reading unit103 and a horizontal element isolation unit 104 while the concentrationof n-type impurity and the concentration of p-type impurity are variedon the completed substrate.

In FIG. 17, parts corresponding to those in FIG. 9 are designated by thesame reference numerals. Similarly, in FIG. 18, parts corresponding tothose in FIGS. 10A to 10D are designated by the same reference numerals.

In the configuration of FIGS. 17 and 18, similarly to the case of FIGS.9 and 10, each vertical transfer register 101 has a smaller width belowthe transfer electrodes 105-2 and 105-3 that are VL electrodes.

Furthermore, in the configuration of FIGS. 17 and 18, unlike the case ofFIGS. 9 and 10, each reading unit 103 and each horizontal elementisolation unit 104 have smaller widths below the transfer electrodes105-2 and 105-3 that are VL electrodes.

For example, in FIG. 17, the width in the horizontal direction of thereading unit 103 has a width W31 at the uppermost portion and thelowermost portion in FIG. 17 but becomes thinner only at the left sidethereof to have a width W32 at a portion at substantially the sameposition in the vertical direction as the upper end of the transferelectrode 105-2 in FIG. 17. The reading unit 103 then extends whilemaintaining the width W32 and becomes thicker to have the original widthW31 at a portion at substantially the same position in the verticaldirection as the lower end of the transfer electrode 105-3 in FIG. 17.

In addition, for example, the width W32 in the horizontal direction ofthe reading unit 103 in FIG. 18B is smaller than the width W31 in thehorizontal direction of the reading unit 103 in FIG. 18D. In contrast,the widths (thicknesses) in the vertical direction of the reading unit103 are the same in FIGS. 18B and 18D.

Furthermore, for example, in FIG. 17, the width in the horizontaldirection of each horizontal element isolation unit 104 has a width W31at the uppermost portion and the lowermost portion thereof in FIG. 17but becomes thinner only at the right side thereof to have a width W32at a portion at substantially the same position in the verticaldirection as the upper end of the transfer electrode 105-2 in FIG. 17.The horizontal element isolation unit 104 then extends while maintainingthe width W32 and becomes thicker to have the original width W31 at aportion at substantially the same position in the vertical direction asthe lower end of the transfer electrode 105-3 in FIG. 17.

In addition, for example, the width W32 in the horizontal direction ofthe horizontal element isolation unit 104 in FIG. 18B is smaller thanthe width W31 in the horizontal direction of the horizontal elementisolation unit 104 in FIG. 18D. In contrast, the widths (thicknesses) inthe vertical direction of the horizontal element isolation unit 104 arethe same in FIGS. 18B and 18D.

Furthermore, for example, the width W21 in the horizontal direction ofthe vertical element isolation unit 102 in FIG. 18A is smaller than thewidth W22 in the horizontal direction of the vertical element isolationunit 102 in FIG. 18C. Thus, as described above with reference to FIG.17, since the reading unit 103 and the horizontal element isolation unit104 have smaller line widths, the width in the horizontal direction inFIG. 17 of the vertical element isolation unit 102 becomes smaller atthe position of the dashed-dotted line A-A′.

In this manner, when each vertical transfer register has a smaller linewidth and each reading unit 103 and each horizontal element isolationunit 104 also have smaller line widths below the VL electrodes, theareas of the light receiving surfaces of the sensor units 108 can bemaintained. In the example of FIG. 17, the areas of the light receivingsurfaces of the sensor units 108 below the VL electrodes are the same asthose in FIG. 2.

With the configuration shown in FIGS. 17 and 18, the same effects asthose of the configuration shown in FIGS. 9 and 10 can still beproduced, and furthermore, the influence of reduction in sensitivity,reduction in saturated signal amount, or the like on the image qualitycan be avoided.

With the configuration shown in FIGS. 17 and 18, however, since eachreading unit 103 and each horizontal element isolation unit 104 havesmaller line widths, the likelihood of occurrence of blooming that isleakage of charge stored in the sensor units 108 into the verticaltransfer registers 101 becomes higher.

FIG. 19 is an enlarged view of part of the imaging unit 22 in FIG. 1 ina form of a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.FIGS. 20A to 20D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 19. FIG. 20A is a cross-sectional viewalong the dashed-dotted line A-A′ in FIG. 19 and FIG. 20B is across-sectional view along the dashed-dotted line B-B′ in FIG. 19.Furthermore, FIG. 20C is a cross-sectional view along the dashed-dottedline C-C′ in FIG. 19 and FIG. 20D is a cross-sectional view along thedashed-dotted line D-D′ in FIG. 19.

In fact, FIG. 19 shows a shape of a mask used in a manufacturing processfor attaching impurity to the substrate, and the configuration of theimaging unit on a completed substrate varies slightly according to themanufacturing process of the substrate. Specifically, similarly to thecase described above with reference to FIGS. 11, 12, etc., each verticaltransfer register 101 is arranged in contact with both of a reading unit103 and a horizontal element isolation unit 104 while the concentrationof n-type impurity and the concentration of p-type impurity are variedon the completed substrate.

In FIG. 19, parts corresponding to those in FIG. 17 are designated bythe same reference numerals. Similarly, in FIG. 20, parts correspondingto those in FIGS. 18A to 18D are designated by the same referencenumerals.

In the configuration shown in FIGS. 19 and 20, similarly to theconfiguration described above with reference to FIGS. 13 and 14, eachvertical transfer register 101 has a smaller line width in such a shapethat only the left side thereof is cut off below the transfer electrodes105-2 and 105-3 that are VL electrodes.

For example, in FIG. 19, the width in the horizontal direction of thevertical transfer register 101 has a width W11 at the uppermost portionand the lowermost portion in FIG. 19 but becomes thinner in such a shapethat only the left side thereof is cut off to have a width W13 at aportion at substantially the same position in the vertical direction asthe upper end of the transfer electrode 105-2 in FIG. 19. The verticaltransfer register 101 then extends while maintaining the width W13 andbecomes thicker to have the original width W11 at a portion atsubstantially the same position in the vertical direction as the lowerend of the transfer electrode 105-3 in FIG. 19.

In addition, for example, the width W13 in the horizontal direction ofthe vertical transfer register 101 in FIG. 20A is smaller than the widthW11 in the horizontal direction of the vertical transfer register 101 inFIG. 20C. Furthermore, the width W13 in the horizontal direction of thevertical transfer register 101 in FIG. 20B is smaller than the width W11in the horizontal direction of the vertical transfer register 101 inFIG. 20D. In contrast, the widths (thicknesses) in the verticaldirection of the vertical transfer register 101 are all the same inFIGS. 20A to 20D.

Furthermore, in the configuration of FIGS. 19 and 20, each horizontalelement isolation unit 104 has a smaller width in such a shape that onlythe right side thereof is cut off below the transfer electrodes 105-2and 105-3 that are VL electrodes.

For example, in FIG. 19, the width in the horizontal direction of eachhorizontal element isolation unit 104 has a width W31 at the uppermostportion and the lowermost portion thereof in FIG. 19 but becomes thinnerin such as shape that only the right side thereof is cut off to have awidth W32 at a portion at substantially the same position in thevertical direction as the upper end of the transfer electrode 105-2 inFIG. 19. The horizontal element isolation unit 104 then extends whilemaintaining the width W32 and becomes thicker to have the original widthW31 at a portion at substantially the same position in the verticaldirection as the lower end of the transfer electrode 105-3 in FIG. 17.

In addition, for example, the width W32 in the horizontal direction ofthe horizontal element isolation unit 104 in FIG. 20B is smaller thanthe width W31 in the horizontal direction of the horizontal elementisolation unit 104 in FIG. 20D. In contrast, the widths (thicknesses) inthe vertical direction of the horizontal element isolation unit 104 arethe same in FIGS. 20B and 20D.

Furthermore, for example, the width W23 in the horizontal direction ofthe vertical element isolation unit 102 in FIG. 20A is smaller than thewidth W22 in the horizontal direction of the vertical element isolationunit 102 in FIG. 20C. Thus, as described above with reference to FIG.19, since each horizontal element isolation unit 104 has a smaller linewidth, the width in the horizontal direction in FIG. 19 of the verticalelement isolation unit 102 becomes smaller at the position of thedashed-dotted line A-A′.

In this manner, when each vertical transfer register has a smaller linewidth and each horizontal element isolation unit 104 also has a smallerline width below the VL electrodes, the areas of the light receivingsurfaces of the sensor units 108 can be maintained. In the example ofFIG. 19, the areas of the light receiving surfaces of the sensor units108 below the VL electrodes are the same as those in FIG. 2.

With the configuration shown in FIGS. 19 and 20, the same effects asthose of the configuration shown in FIGS. 13 and 14 can be produced, andfurthermore, the influence of reduction in sensitivity, reduction insaturated signal amount, or the like on the image quality can beavoided.

With the configuration shown in FIGS. 19 and 20, however, since eachhorizontal element isolation unit 104 has a smaller line width, thelikelihood of occurrence of blooming that is leakage of charge stored inthe sensor units 108 into the vertical transfer registers 101 becomeshigher. With the configuration shown in FIGS. 19 and 20, however, sinceeach reading unit 103 does not have a smaller line width, the likelihoodof occurrence of blooming can be deemed to be lower than theconfiguration shown in FIGS. 17 and 18.

While a configuration in which each vertical transfer register has asmaller line width and only each horizontal element isolation unit 104also has a smaller line width under the VL electrodes has been explainedin FIGS. 19 and 20, a configuration in which each vertical transferregister has a smaller line width and only each reading unit 103 has asmaller line width may be used. A configuration in this case is shown inFIGS. 21 and 22. Detailed description thereof is not provided herein.

Methods of reducing the amount of doped n-type impurity by making theline width of each vertical transfer register 101 below VL electrodessmaller to suppress occurrence of white flaws have been described above.The amount of doped n-type impurity may be reduced by lowering theconcentration of n-type impurity forming each vertical transfer register101 below VL electrodes, for example. A configuration in this case isshown in FIGS. 23 and 24.

FIG. 23 is an enlarged view of part of the imaging unit 22 in FIG. 1 ina form of a plan view showing an example configuration of an imagingunit according to still another embodiment of the present technology.FIGS. 24A to 24D show cross-sectional views along dashed-dotted linesA-A′, B-B′, C-C′ and D-D′ in FIG. 23. FIG. 24A is a cross-sectional viewalong the dashed-dotted line A-A′ in FIG. 23 and FIG. 24B is across-sectional view along the dashed-dotted line B-B′ in FIG. 23.Furthermore, FIG. 24C is a cross-sectional view along the dashed-dottedline C-C′ in FIG. 23 and FIG. 24D is a cross-sectional view along thedashed-dotted line D-D′ in FIG. 23.

In fact, FIG. 23 shows a shape of a mask used in a manufacturing processfor attaching impurity to the substrate, and the configuration of theimaging unit on a completed substrate varies slightly according to themanufacturing process of the substrate. Specifically, similarly to thecase described above with reference to FIGS. 11, 12, etc., each verticaltransfer register 101 is arranged in contact with both of a reading unit103 and a horizontal element isolation unit 104 while the concentrationof n-type impurity and the concentration of p-type impurity are variedon the completed substrate.

In FIG. 23, parts corresponding to those in FIG. 9 are designated by thesame reference numerals. Similarly, in FIG. 24, parts corresponding tothose in FIGS. 10A to 10D are designated by the same reference numerals.

In the configuration shown in FIGS. 23 and 24, unlike the configurationdescribed above with reference to FIGS. 9 and 10, the line width of eachvertical transfer register 101 below the transfer electrodes 105-2 and105-3 that are VL electrodes is not decreased. Instead, theconcentration of n-type impurity forming each vertical transfer resister101 arranged below the transfer electrodes 105-2 and 105-3 is lowered.In FIGS. 23 and 24, the difference in concentration of n-type impurityis expressed by changing the hatching pattern of the vertical transferregisters 101.

In the configuration shown in FIGS. 23 and 24, since the features otherthan those described above are the same as those described withreference to FIGS. 9 and 10, detailed description thereof will not berepeated.

FIG. 25 is a cross-sectional view in the longitudinal direction ofvertical transfer registers 101 along a dashed-dotted line E-E′ in FIG.23. As shown in FIG. 25, an n-type impurity region 101 b below thetransfer electrodes 105-2 and 105-3 that are VL electrodes has a lowern-type impurity concentration than the other n-type impurity regions 101a. Specifically, the concentration of n-type impurity for forming eachn-type impurity region 101 a and that of n-type impurity for formingeach n-type impurity region 101 b are different in manufacturing thesubstrate.

FIGS. 26A and 26B show cross-sectional views for explaining theconfiguration of an imaging unit on a completed substrate takingimpurity dispersion in the manufacturing process into considerationsimilarly to FIG. 11. FIG. 26A is a cross-sectional view along thedashed-dotted line B-B′ in FIG. 23 and corresponds to FIG. 24B. FIG. 26Bis a cross-sectional view along the dashed-dotted line D-D′ in FIG. 23and corresponds to FIG. 24D.

While each vertical transfer register 101 and each reading unit 103 aredrawn as being arranged separately from each other in FIGS. 24B and 24D,the vertical transfer register 101 and the reading unit 103 are drawn asbeing in contact with each other in FIGS. 26A and 26B. Furthermore,while each vertical transfer register 101 and each horizontal elementisolation unit 104 are drawn as being arranged separately from eachother in FIGS. 24B and 24D, each vertical transfer register 101 and eachhorizontal element isolation unit 104 are drawn as being in contact witheach other in FIGS. 26A and 26B.

Thus, as a result of impurity dispersion in the manufacturing process,the n-type impurity regions (vertical transfer registers 101) and thep-type impurity regions (reading units 103 and horizontal elementisolation units 104) have dispersed. When impurity is attached by usingthe mask as shown in FIG. 23, however, the concentration of n-typeimpurity is high at the center of the line of each vertical transferregister 101 and becomes lower toward both ends thereof, for example.Furthermore, the concentration of p-type impurity is high at the centerof the line of each reading unit 103 or each horizontal elementisolation unit 104 and becomes lower toward both ends thereof.

In FIG. 26, the state in which the concentration of n-type impurity ishigh at the center of the line of each vertical transfer register 101and becomes lower toward both ends thereof is expressed by a gradation.Similarly, the state in which the concentration of p-type impurity ishigh at the center of the line of each reading unit 103 or eachhorizontal element isolation unit 104 and becomes lower toward both endsthereof is expressed by a gradation.

FIG. 27 is a graph explaining variation in the impurity concentrationdescribed above. In FIG. 27, the horizontal axis represents the positionin the horizontal direction in FIGS. 26A and 26B and the vertical axisrepresents the impurity concentration.

In FIG. 27, a solid line 221 represents variation in the concentrationof n-type impurity at a dashed-dotted line F-F′ in FIG. 26A, and adotted line 222 represents variation in the concentration of n-typeimpurity at a dashed-dotted line G-G′ in FIG. 26B. Note that theconcentration of n-type impurity around the center in FIG. 27 representsthe concentration of n-type impurity of the vertical transfer register101, and the concentrations of n-type impurity around the left and rightends in FIG. 27 represent the concentrations of n-type impurity of thesensor units 108.

Furthermore, in FIG. 27, a solid line 223 represents variation in theconcentration of p-type impurity at the dashed-dotted line F-F′ in FIG.26A, and a dotted line 224 represents variation in the concentration ofp-type impurity at the dashed-dotted line G-G′ in FIG. 26B. Note thatthe solid line 223 and the dotted line 224 represent the concentrationsof p-type impurity of the horizontal element isolation unit 104.

The solid line 223 changes more sharply than the dotted line 224.Specifically, the solid line 223 and the dotted line 224 both form peaksat a point on the left side in FIG. 27 and incline gently leftward andrightward therefrom, and the inclination of the solid line 223 issharper.

Furthermore, in FIG. 27, a solid line 225 represents variation in theconcentration of p-type impurity at the dashed-dotted line F-F′ in FIG.26A, and a dotted line 226 represents variation in the concentration ofp-type impurity at the dashed-dotted line G-G′ in FIG. 26B. Note thatthe solid line 225 and the dotted line 226 represent the concentrationsof p-type impurity of the reading unit 103.

The solid line 225 changes more sharply than the dotted line 226.Specifically, the solid line 225 and the dotted line 226 both form peaksat a point on the right side in FIG. 27 and incline gently leftward andrightward therefrom, and the inclination of the solid line 225 issharper.

With the configuration of the imaging unit 22 as described above withreference to FIGS. 23 to 27, the influence of white flaws can still bereduced without preventing the decrease in the pixel size of solid-stateimage sensors.

Specifically, with the configuration of FIGS. 23 and 24, the n-typeimpurity concentration of the vertical transfer registers is made lowerbelow the VL electrodes where occurrence of white flaws having influenceon the image quality is significant. As a result, the amount of dopedn-type impurity below VL electrodes is reduced and the amount of n-typeimpurity per unit area becomes smaller below the VL electrodes on thecompleted substrate, which can suppress occurrence of white flaws havinginfluence on the image quality. Thus, the total amount of n-typeimpurity below the VL electrodes is reduced.

At the same time, with the present technology, the centers of the linesof the reading units 103 and the horizontal element isolation units 104are farther from the vertical transfer registers below the VLelectrodes. As a result, the vertical transfer registers 101 become lesslikely to be influenced by dispersion of p-type impurity of the adjacentreading units 103 and horizontal element isolation units 104, and thepotential can be made sufficiently deep even with the reduced amount ofdoped n-type impurity. Thus, a desired potential can be obtained evenwhen the n-type impurity concentration of the vertical transferregisters 101 is lowered.

While it is explained in FIG. 25 that the concentration of n-typeimpurity for forming each n-type impurity region 101 a and that ofn-type impurity for forming each n-type impurity region 101 b aredifferent in manufacturing the substrate, a manufacturing methoddifferent therefrom may be used. A manufacturing method different fromthat in FIG. 25 will be described with reference to FIG. 28.

FIG. 28 is a cross-sectional view in the longitudinal direction ofvertical transfer registers 101 along a dashed-dotted line E-E′ in FIG.23. In this example, an n-type impurity region 101 d having a relativelylow concentration is formed below all the transfer electrodes 105, andan n-type impurity region 101 c having a relatively high concentrationis formed thereon. The n-type impurity region 101 c, however, is notformed below the transfer electrodes 105-2 and 105-3 that are VLelectrodes.

Specifically, in the case of FIG. 28, an n-type impurity region formingeach vertical transfer register 101 is constituted by two layers but onelayer of n-type impurity region lies below the VL electrodes.

As a result of using the manufacturing method as described above withreference to FIG. 28, the substrate can be manufactured more easily thanthe case of FIG. 25, for example. Specifically, while a considerablyhigh technology level is required to reproduce the n-type impurityregion 101 b at a highly accurate position in the case of FIG. 25, sucha high technology level is not required for the manufacture as in FIG.28.

Note that, with the configuration described above with reference toFIGS. 9 and 10, the areas of the light receiving surfaces of the sensorunits 108 below the VL electrodes are reduced. As a result, although theinfluence on the entire solid-state image sensor is considered to beminor, there is a concern about influence of reduction in saturatedsignal amount or the like. For example, the reduction in saturatedsignal amount can be suppressed by additionally doping n-type impurityinto the n-type impurity regions corresponding to the sensor units belowthe VL electrodes.

As shown in FIG. 29, for example, n-type impurity may be additionallydoped into the n-type impurity regions corresponding to the sensor unitsbelow the VL electrodes. In FIG. 29, parts corresponding to those inFIG. 9 are designated by the same reference numerals.

In the example of FIG. 29, n-type impurity is additionally doped intothe sensor units 108-11 and 108-21 arranged below the transferelectrodes 105-2 and 105-3 that are VL electrodes among multiple sensorunits. In FIG. 29, the additional doping of n-type impurity is expressedby hatching of the sensor units 108-11 and 108-21. Since theconfiguration of the other parts in FIG. 29 is the same as that in FIG.9, detailed description thereof will not be repeated.

With the configuration as shown in FIG. 29, the potential of the sensorunits 108-11 and 108-21 can be made sufficiently deep, and reduction insaturated signal amount can be suppressed.

Similarly, with the configurations described above with reference toFIGS. 13, 15, and 23, the reduction in saturated signal amount can besuppressed by additionally doping n-type impurity into the n-typeimpurity regions corresponding to the sensor units below the VLelectrodes.

While an example in which the reduction in saturated signal amount issuppressed by additionally doping n-type impurity is described herein,the reduction in saturated signal amount can also be suppressed bychanging the amount of p-type impurity doped in the surfaces of thesensor units 108-11 and 108-21.

While the configuration of the imaging unit 22 suitable for chargetransfer when a moving image is captured is described above withreference to FIGS. 4 to 6, the present technology may be applied to aconfiguration of the imaging unit 22 suitable for charge transfer when astatic image is captured, for example.

FIG. 30 is a timing chart of charge transfer when a static image iscaptured by the solid-state imaging device 10. Similarly to FIG. 4, FIG.30 shows waveforms of the transfer clock signals φV1 to φV8. In FIG. 30,vertical lines actually represent pulses of the signals.

The waveforms of the transfer clock signals φV1 to φV8 change to voltagevalues of H (high-level voltage), M (middle-level voltage), and L(low-level voltage). For each of the signals, a part represented by ahorizontal line corresponds to a standby voltage.

As shown in FIG. 30, the transfer clock signals φV1 to φV8 are appliedto the transfer electrodes with phases shifted periodically. Thevertical transfer registers are controlled by the transfer clock signalsapplied to the transfer electrodes so that the potential distribution ofthe potential well changes sequentially, and function as what are calledshift registers configured to transfer the charges in the potential wellin the phase shift direction of the transfer clock signals.

FIG. 31 is chart corresponding to FIG. 5 in a form of an enlarged chartof waveforms of the transfer clock signals φV1 to φV8 in FIG. 30. Inthis example, the waveforms of the transfer clock signals φV1 to φV8 attime t0 to time t8 are shown. As shown in FIG. 31, the transfer clocksignals φV1 to φV8 are pulsed with shifted phases.

FIG. 32 is a chart corresponding to FIG. 6, and shows potentials of thetransfer electrodes at time t0 to time t8 in FIG. 31. Note that thetransfer electrodes to which the transfer clock signals φV1 to φV8 areapplied are referred to as transfer electrodes V1 to V8, respectively.In FIG. 31, parts shown by thick black horizontal lines represent thepotential well, and parts shown as white projections represent potentialbarriers.

As shown in FIGS. 30 to 32, in charge transfer when a static image iscaptured, the transfer electrodes V1, V7, and V8 are VL electrodes, andthe transfer electrodes V2 to V6 are VM electrodes.

Thus, in the case where the present technology is applied to aconfiguration of the imaging unit 22 suitable for charge transfer when astatic image is captured, the number of VL electrodes needs to be set tothree in the configurations described above with reference to FIG. 9,etc. In addition, the configurations of the vertical transfer registers101, the reading units 103 and the horizontal element isolation units104 below the three VL electrodes may be according to the embodimentsdescribed above.

Furthermore, the number of VL electrodes may change depending on thedesign of the device, the present technology can still be applied tosuch cases.

Note that the present technology is not limited to application tosolid-state image sensors such as CCD image sensors. Specifically, thepresent technology can be applied to all aspects of electronic devicesusing solid-state image sensors in image capturing units (photoelectricconversion units) such as imaging devices such as digital still camerasand video cameras, portable terminal devices having imaging functions,and copiers using solid-state image sensors in image capturing units. Asolid-state image sensor may be in a form of one-chip, a form in whichmultiple chips are stacked or arranged adjacent to one another, or amodular form having an imaging function in which an imaging unit, asignal processor or an optical system are packaged together.

FIG. 33 is a block diagram showing an example configuration of a cameradevice that is an electronic device to which the present technology isapplied.

The camera device 600 in FIG. 33 includes an optical unit 601 includinga lens group and the like, a solid-state imaging device (imaging device)602 having the configurations of pixels 2 described above, and a DSPcircuit 603 that is a camera signal processing circuit. The cameradevice 600 also includes a frame memory 604, a display unit 605, arecording unit 606, an operation unit 607, and a power supply unit 608.The DSP circuit 603, the frame memory 604, the display unit 605, therecording unit 606, the operation unit 607, and the power supply unit608 are connected to one another via a bus line 609.

The optical unit 601 receives incident light (image light) from asubject, and focuses the light on an imaging plane of the solid-stateimaging device 602. The solid-state imaging device 602 converts theamount of incident light focused on the imaging plane by the opticalunit 601 into electric signals in unit of pixels and outputs theelectric signals as pixel signals. A solid-state image sensor such as aCCD image sensor in which multiple unit pixels according to theembodiments described above are arranged can be used as the solid-stateimaging device 602.

The display unit 605 is a panel display device such as a liquid crystalpanel or an organic EL (electroluminescence) panel, and displays movingimages or static images captured by the solid-state imaging device 602.The recording unit 606 records the moving images or static imagescaptured by the solid-state imaging device 602 on a recording mediumsuch as a video tape, or a DVD (digital versatile disk).

The operation unit 607 issues operation instructions on variousfunctions of the camera device 600 according to user's operations. Thepower supply unit 608 supplies various powers to be operating powers forthe DSP circuits 603, the frame memory 604, the display unit 605, therecording unit 606, and the operation unit 607 to these components towhich power is to be supplied where necessary.

As described above, as a result of using the solid-state imaging device10 according to the embodiments described above as the solid-stateimaging device 602, white flaws can be made unnoticeable even with areduced cell size, which can improve the image quality of imagescaptured by the camera device 600 such as a video camera and a digitalstill camera, and furthermore, a camera module for mobile devices suchas portable phones.

In addition, the present technology is not limited to application tosolid-state image sensors configured to detect distribution of theamount of incident visible light and capture the light distribution asan image, but can be applied to all aspects of solid-state image sensorsconfigured to capture distribution of the amount of incident infraredrays, X rays, particles, or the like as an image, and in a broadersense, solid-state image sensors (physical quantity distributiondetecting devices) such as fingerprint sensors configured to detectdistribution of other physical quantities such as pressure andcapacitance.

Furthermore, the embodiments of the present technology are not limitedto those described above, but various modifications may be made theretowithout departing from the scope of the present technology.

The present technology can also have the following configurations.

(1)

A solid-state image sensor including:

a register unit configured to transfer charge stored in a photoelectricconversion unit and formed as an n-type impurity region extending in afirst direction;

a reading unit configured to read charge from the photoelectricconversion unit into the register unit and formed as a p-type impurityregion extending in the same direction as the register unit;

a horizontal element isolation unit configured to prevent leakage ofcharge from the photoelectric conversion unit and formed as a p-typeimpurity region extending in the same direction as the register unit;and

multiple transfer electrodes configured to apply voltage for changingpotential distribution of the register unit, wherein

a total amount of n-type impurity forming the register unit below alow-level electrode having a standby voltage of a predetermined lowvalue among the transfer electrodes is smaller than a total amount ofn-type impurity forming the register unit below a middle-level electrodehaving a standby voltage higher than the predetermined low value.

(2)

The solid-state image sensor of (1), wherein in the second directionperpendicular to the first direction, a width of n-type impurity formingthe register unit below the low-level electrode is smaller than a widthof n-type impurity forming the register unit below the middle-levelelectrode.

(3)

The solid-state image sensor of (1), wherein a concentration of n-typeimpurity forming the register unit below the low-level electrode islower than a concentration of n-type impurity forming the register unitbelow the middle-level electrode.

(4)

The solid-state image sensor of any one (1) to (3), wherein in thesecond direction perpendicular to the first direction, a highestconcentration position below the low-level electrode is closer to thephotoelectric conversion unit than a highest concentration positionbelow the middle-level electrode, the highest concentration positionsbeing positions where impurity concentration of the p-type impurityregion forming the reading unit or the horizontal element isolation unitis highest.

(5)

The solid-state image sensor of (4), wherein only for highestconcentration positions in the p-type impurity region forming thereading unit among the highest concentration positions, the highestconcentration position below the low-level electrode is closer to thephotoelectric conversion unit than the highest concentration positionbelow the middle-level electrode.

(6)

The solid-state image sensor of (4), wherein only for highestconcentration positions in the p-type impurity region forming thehorizontal element isolation unit among the highest concentrationpositions, the highest concentration position below the low-levelelectrode is closer to the photoelectric conversion unit than thehighest concentration position below the middle-level electrode.

(7)

The solid-state image sensor of any one of (1) to (6), wherein n-typeimpurity concentration of the sensor unit at a position corresponding tothat of the low-level electrode is higher than n-type impurityconcentration of the sensor unit at a position corresponding to that ofthe middle-level electrode.

(8)

The solid-state image sensor of any one of (1) to (6), wherein p-typeimpurity concentration of a surface of the sensor unit at a positioncorresponding to that of the low-level electrode is lower than p-typeimpurity concentration of a surface of the sensor unit at a positioncorresponding to that of the middle-level electrode.

(9)

A solid-state imaging device including:

a register unit configured to transfer charge stored in a photoelectricconversion unit and formed as an n-type impurity region extending in afirst direction;

a reading unit configured to read charge from the photoelectricconversion unit into the register unit and formed as a p-type impurityregion extending in the same direction as the register unit;

a horizontal element isolation unit configured to prevent leakage ofcharge from the photoelectric conversion unit and formed as a p-typeimpurity region extending in the same direction as the register unit;

multiple transfer electrodes configured to apply voltage to the registerunit; and

a timing generation circuit configured to supply voltage to the transferelectrodes to change potential distribution of the register unit,wherein

a total amount of n-type impurity forming the register unit below alow-level electrode having a standby voltage of a predetermined lowvalue among the transfer electrodes is smaller than a total amount ofn-type impurity forming the register unit below a middle-level electrodehaving a standby voltage higher than the predetermined low value.

(10)

A camera device including:

a solid state image sensor including:

-   -   a register unit configured to transfer charge stored in a        photoelectric conversion unit and formed as an n-type impurity        region extending in a first direction;    -   a reading unit configured to read charge from the photoelectric        conversion unit into the register unit and formed as a p-type        impurity region extending in the same direction as the register        unit;    -   a horizontal element isolation unit configured to prevent        leakage of charge from the photoelectric conversion unit and        formed as a p-type impurity region extending in the same        direction as the register unit; and    -   multiple transfer electrodes configured to apply voltage for        changing potential distribution of the register unit, wherein    -   a total amount of n-type impurity forming the register unit        below a low-level electrode having a standby voltage of a        predetermined low value among the transfer electrodes is smaller        than a total amount of n-type impurity forming the register unit        below a middle-level electrode having a standby voltage higher        than the predetermined low value;

an optical system configured to guide incident light to the solid stateimage sensor; and

a signal processing circuit configured to process an image signal outputfrom a solid-state image sensor.

(11)

The camera device of (10), further including a display unit configuredto display an image captured by the solid-state imaging device.

(12)

The camera device of (10) or (11), further including a recording unitconfigured to record data of an image captured by the solid-stateimaging device.

(13)

A camera device of any one of (10) to (12), further including anoperation unit configured to generate a signal in response to anoperation instruction according to a user's operation.

REFERENCE SIGNS LIST

-   10 Solid-state imaging device-   11 CCD image sensor-   12 Timing generation circuit-   22 Imaging unit 22-   23 Horizontal transfer register-   24 Output unit-   101 Vertical transfer register-   102 Vertical element isolation unit-   103 Reading unit-   104 Horizontal element isolation unit-   105 Transfer electrode-   108 Sensor unit-   110 Substrate

What is claimed is:
 1. A solid-state image sensor comprising: a registerunit configured to transfer charge stored in a photoelectric conversionunit and formed as an n-type impurity region extending in a firstdirection; a reading unit configured to read charge from thephotoelectric conversion unit into the register unit and formed as ap-type impurity region extending in the same direction as the registerunit; a horizontal element isolation unit configured to prevent leakageof charge from the photoelectric conversion unit and formed as a p-typeimpurity region extending in the same direction as the register unit;and multiple transfer electrodes configured to apply voltage forchanging potential distribution of the register unit, wherein a totalamount of n-type impurity forming the register unit below a low-levelelectrode having a standby voltage of a predetermined low value amongthe transfer electrodes is smaller than a total amount of n-typeimpurity forming the register unit below a middle-level electrode havinga standby voltage higher than the predetermined low value.
 2. Thesolid-state image sensor according to claim 1, wherein in the seconddirection perpendicular to the first direction, a width of n-typeimpurity forming the register unit below the low-level electrode issmaller than a width of n-type impurity forming the register unit belowthe middle-level electrode.
 3. The solid-state image sensor according toclaim 1, wherein a concentration of n-type impurity forming the registerunit below the low-level electrode is lower than a concentration ofn-type impurity forming the register unit below the middle-levelelectrode.
 4. The solid-state image sensor according to claim 1, whereinin the second direction perpendicular to the first direction, a highestconcentration position below the low-level electrode is closer to thephotoelectric conversion unit than a highest concentration positionbelow the middle-level electrode, the highest concentration positionsbeing positions where impurity concentration of the p-type impurityregion forming the reading unit or the horizontal element isolation unitis highest.
 5. The solid-state image sensor according to claim 4,wherein only for highest concentration positions in the p-type impurityregion forming the reading unit among the highest concentrationpositions, the highest concentration position below the low-levelelectrode is closer to the photoelectric conversion unit than thehighest concentration position below the middle-level electrode.
 6. Thesolid-state image sensor according to claim 4, wherein only for highestconcentration positions in the p-type impurity region forming thehorizontal element isolation unit among the highest concentrationpositions, the highest concentration position below the low-levelelectrode is closer to the photoelectric conversion unit than thehighest concentration position below the middle-level electrode.
 7. Thesolid-state image sensor according to claim 1, wherein n-type impurityconcentration of the sensor unit at a position corresponding to that ofthe low-level electrode is higher than n-type impurity concentration ofthe sensor unit at a position corresponding to that of the middle-levelelectrode.
 8. The solid-state image sensor according to claim 1, whereinp-type impurity concentration of a surface of the sensor unit at aposition corresponding to that of the low-level electrode is lower thanp-type impurity concentration of a surface of the sensor unit at aposition corresponding to that of the middle-level electrode.
 9. Asolid-state imaging device comprising: a register unit configured totransfer charge stored in a photoelectric conversion unit and formed asan n-type impurity region extending in a first direction; a reading unitconfigured to read charge from the photoelectric conversion unit intothe register unit and formed as a p-type impurity region extending inthe same direction as the register unit; a horizontal element isolationunit configured to prevent leakage of charge from the photoelectricconversion unit and formed as a p-type impurity region extending in thesame direction as the register unit; multiple transfer electrodesconfigured to apply voltage to the register unit; and a timinggeneration circuit configured to supply voltage to the transferelectrodes to change potential distribution of the register unit,wherein a total amount of n-type impurity forming the register unitbelow a low-level electrode having a standby voltage of a predeterminedlow value among the transfer electrodes is smaller than a total amountof n-type impurity forming the register unit below a middle-levelelectrode having a standby voltage higher than the predetermined lowvalue.
 10. A camera device comprising: a solid state image sensorincluding: a register unit configured to transfer charge stored in aphotoelectric conversion unit and formed as an n-type impurity regionextending in a first direction; a reading unit configured to read chargefrom the photoelectric conversion unit into the register unit and formedas a p-type impurity region extending in the same direction as theregister unit; a horizontal element isolation unit configured to preventleakage of charge from the photoelectric conversion unit and formed as ap-type impurity region extending in the same direction as the registerunit; and multiple transfer electrodes configured to apply voltage forchanging potential distribution of the register unit, wherein a totalamount of n-type impurity forming the register unit below a low-levelelectrode having a standby voltage of a predetermined low value amongthe transfer electrodes is smaller than a total amount of n-typeimpurity forming the register unit below a middle-level electrode havinga standby voltage higher than the predetermined low value; an opticalsystem configured to guide incident light to the solid state imagesensor; and a signal processing circuit configured to process an imagesignal output from a solid-state image sensor.
 11. The camera deviceaccording to claim 10, further comprising a display unit configured todisplay an image captured by the solid-state imaging device.
 12. Thecamera device according to claim 10, further comprising a recording unitconfigured to record data of an image captured by the solid-stateimaging device.
 13. A camera device according to claim 10, furthercomprising an operation unit configured to generate a signal in responseto an operation instruction according to a user's operation.